A sensor, a
system of direct measurement using that sensor, and a method of direct and simultaneous measurement of
conductivity and
dielectric constant of a fluid, particularly
high impedance,
hydrocarbon-based fluids. The sensor has a
cell that holds the fluids to be measured between a
single pair of coaxial,
bare metal electrodes connected through interface circuitry to measurement circuitry preferably implemented in one or several IC's. The sensor has a mutually compatible
electrode geometry that provides both the correct
cell constant for measurement of
conductivity of hydrocarbons fluids (typical range 0-100,000 pS / cm), and a bulk
capacitance (for use in
dielectric constant measurement) in the range of measure of readily available low cost commercial IC's (having a typical
capacitance measurement span of <10 pF, with a total bulk
capacitance at the
chip of <20 pF). The
cell conductivity constant for use with
hydrocarbon-based oils having a conductivity in the range of 1 to 500,000 pS / M is preferably less than or equal to about 0.1. The cell bulk capacitance with
hydrocarbon fluids inside the sensor results in a bulk capacitance of at least about 4 pF. In one embodiment, the electronic circuitry is a
Microcontroller / DSP that both generates synchronous drive signals at various frequencies, for both conductivity and
dielectric constant measurements while directly digitizing and numerically
processing the sensor output.